Centrifugal governor switch



April 1959 w. E. RHODES ETAL 2,884,496

CENTRIFUGAL GOVERNOR SWITCH Filed April K18, 1957 II 4 8? i=1 7 5 INVENTORS )lfz/m f/a aoes ATTORNEY United States Patent CENTRIFUGAL GOVERNOR SWITCH William E. Rhodes and Clarence D. Roe, Columbus,

Ohio, assignors to Robertshaw-Fulton Controls Company, Greensburg, Pa., a corporation of Delaware Application April 18, 1957, Serial No. 653,581

12 Claims. (Cl. 200-80) This invention relates to a switch device, and more particularly to a novel snap acting centrifugal switch for governing devices like motors and generators which operate at very high rotational speeds in the order of 10,000 to 15,000 rpm.

Governor switches for cutting in and cutting out starting windings of electrical motors and generators are well known. However, almost all previous devices have utilized a governing actuator mass which operates some type of switching mechanism when a certain angular velocity is reached.

At high rotational speeds, for example, 8,000 to 10,000 r.p.m. or more, the actuator mass used in previous governor switch devices exerts such a high force that such an actuator mass cannot be satisfactorily used. As a result, efforts have been made to design a high speed centrifugal speed control switch device which does not use such a mass actuator. It has been proposed to substitute a control switch utilizing a heavy flexible contact carrying arm designed to break contact with a fixed contact when a predetermined speed is reached.

Generally this prior type governor device includes a switch comprising a heavy biased arm which is cantilevermounted at one end on a base and carries at its other end a moving contact that cooperates with a fixed contact on the base. When a shaft on which the governor device is mounted rotates above a predetermined speed, the centrifugal force exerted on the relatively heavy contact arm causes it to pivot away from the axis of the shaft, thereby separating the contacts. The contact arm is normally biased to a closed position as the rotary speed of the shaft decreases. However, several major problems are inherent in this type of centrifugal switch including, among others: low or erratic contact pressure prior to the point of contact break, with resulting destructive arcing across the switch contacts; inaccurate adjustment means; lack of positive control of switch operating characteristics; and inability to get close control of rotational speed. These and other shortcomings and disadvantages of this prior attempt to meet the above-discussed need in the art are overcome by the present invention, as will hereinafter appear.

It is a principal object of this invention to provide a novel snap acting switch device which can be used as a governor for all types of rotating machinery, and is especially suitable for governing devices like motors and generators operating at very high r.p.rn.

Another object of this invention is to provide a novel snap acting switch which in itself constitutes the speed governor, and does not utilize an external centrifugal mass as actuator. It is a related object of the present invention to provide such a snap acting governor switch which is positive in its switching action and has good controllable precision snap acting switch characteristics.

Still another object of this invention is to provide a governing type snap acting switch which maintains high contact pressure up to the point of contact break and thus greatly reduces destructive arcing.

2,884,496 Patented Apr. 28, 19 59 It is another object of this invention to provide a novel centrifugal snap acting switch device incorporating a snapover contact and follow-up contact which moves to the snapover point with it, thereby providing increasingly high contact pressure up to the point of contact break. It is a related object of this invention to provide such a snap switch governor device in which the centrifugal force on the follow-up and snapover blades, and contacts thereon, acts in conjunction with the change in flexure of the snapover contact blade to provide instantaneous break of the contacts at a point of maximum contact pressure.

Yet another object of the present invention is to provide a novel snap acting governor switch which can be readily adjusted to maintain within close limits the rotational speed of the motor, generator or like device which the switch is to control.

Other objects and advantages of the present invention will become apparent from the following description and claims, and the accompanying drawings wherein:

Fig. 1 is an elevation view of the novel centrifugal snap acting switch of this invention, looking along the rotational axis of the switch;

Fig. 2 is a partial sectional view along line 2-2 in Fig. 1, showing the relation of switch parts to the slipring connections provided on the switch;

Fig. 3 is a detailed sectional view of the end of the snapover operating contact blade and supporting bracket, taken along line 3-3 in Fig. 1;

Fig. 4 is a detailed side view of the snapover operating contact member looking in the direction of arrow 4 in Fig. 1; and

Fig. 5 is a detailed view of the follow-up blade connection.

Referring more particularly to Figs. 1 and 2, a governor device 30 includes two switch units generally designated 36 and 38, mounted on a base 40 of dielectric material, which is designed to be mounted in turn on a motor, generator or like shaft 34 for rotation about axis Y. However, it should be understood that only one of the switches 36 and 38 might be used in certain applications, as will be apparent hereinafter.

Each switch unit includes a bracket 42 which is mounted on the base 40 by rivets 44 and 45, or like means. Bracket 42 has an upstanding L-shaped leg 46 to which is threadedly connected an adjustable contact stop screw 48 and a blade compression adjustment screw 50, each having a suitable lock nut means 49 and 51, respectively. An operating blade 52 carrying a snapover contact 54 is mounted for snap movement in the ends of a U- shaped bracket 56, which in turn is attached to the leg 46 of bracket 42 by rivets 57, or the like. The operating blade 52 is biased toward the shaft center Y and its outer ends are compressed between the ends of U-bracket 56. Referring also now to Figs. 3 and 4, the operating blade 52 has reduced ends 58 which are received in slots 60 in the ends of U-shaped bracket 56. This provides a relatively friction-free connection between the operating blade 52 and bracket 56 and retains the parts in operative association with each other, while permitting snap action of operating blade 52 as hereinafter described.

A follow-up contact blade 62 and a backing leaf spring stop 64 are mounted adjacent to the operating snapover blade 52, as shown in Fig. 1. The follow-up contact blade 62 is supported between two like brackets 66 which are fastened to base 40 by rivets 70 or like means. One end of follow-up blade 62 is immovably attached to bracket 66 by rivets 72. The other end is loosely connected to, but held in confinement in, an aperture in adjustable leaf member 74 which is suitably mounted on bracket 66. As shown particularly in Fig.

seesaw '5, the end 76 of follow-up blade 62 has a notched portion 78 which is' inserted in undersiie slot"80 in 'brackt 74. This permits the follow-up contact blade 62 to follow the operating snapover blade 52 until its notched end 82 engages theleaf 74. The follow up blade'62 carries a contact 63 in opposed relation to contact 54 on the operating snapover blade 52. The backup spring 64 presses follow-up contact 63 against snapover contact 54 to prevent them from separating when theswitch device 30 is in a static condition. V i i In operation, as the rotational speed of shaft 34 is increased, the operating blade 52 tends to move away from the center Y due to centrifugal force exe rted thereon. During this movement, the follow-up contact blade 62 and the backdrop spring stop 64 move together with the operating blade 52 under centrifugal force. This follow-up and good contact pressure can be assured by making the follow-up contact 63 and blade 62 of slightly greater mass than operating contacf 4 and blade 52, with appropriate mass and bias for the backup leaf 64. When the desired angular velocity is reachedfthe operating blade 52 snaps through center so'that contact 54 then abuts against the adjustable stop 4%. Continuity be: tween the snapover contact 54 and the follow-up contact 63 is broken when this snap action of blade 52 occurs because the follow-up blade 62 is prevented from further movement by engagement of its notched end 82 against the bracket leaf 74 as explained above. As the angular velocity of shaft 34 is reduced, the operating blade 52, being biased toward the center Y, moves away from the stop 48 and finally snaps over so that contact 54 again engages contact 63 on the follow-up blade.

Three adjustment means indicated at 48, 50 and 84, respectively, are provided for adjustment and control of the operating characteristics of switches 36 and 38 and the rotational speed at which they operate with the abovedescribed snap action. Adjustment of screw means 48 on either of switches 36 or 38 changes the total travel of the corresponding operating blade 52. Greater travel of blade 52 causes it to return more slowly to the central position shown in Fig; 1 from abutment against screw 48 after snapover, as the angular velocity of shaft 34 is reduced. Adjustment means 50 on switches 36 and 38, respectively, bends one end of the U-shaped member 56 toward its other end, or permits the ends to separate if the screw is backed oft, thereby changing the bias of the operating blade 52. The eifect of this adjustment is to change the angular velocity at which the operating blade 52 is actuated as a result of centrifugal force, since a higher velocity is required as the bias of the blade is increased. The third adjustment 84 increases or decreases the extent of movement of followup blade 62 together with operating blade 52 under the action of centrifugal force, by changing the point at which notched end 32 of follow-up blade 62 engages leaf members '74. This adjustment therefore changes the point at which the contact 54 on operating snapover blade 52 breaks from the follow-up contact 63 at increasing rotational speed and again makes contact upon decreasing rotational speed. Locking means for adjustments 48, 50 and 84 are provided through locknuts 4 9, 51 and 85, respectively.

Electrical operation of the centrifugal switch governor device 30 can best be explained and understood by referring to Figs. 2 and 1. Three slip rings 86, 88 and 90, are provided to make electrical connection with portions of a conventional system that does not form a part of this invention. The bracket 42 and operating blade 52 of the switch 36 are electrically connected to outer slip ring 86 by rivets 44 made of a highly conductive material, such as silver, so that electrical energy can be transmitted from the slip ring 86 to contact 54 on operating blade 52 of switch 36. Middle slip ring 88 is also similarlyconnectcd bymeans of rivets 45 to the bracket 42 and operating contact 54 of switch 38. A similar connection is made through rivets 70 and brackets 66 between the central slip "ring and follow-up blades 64 of switches 36 and 38. An electrical circuit is thus made between slip rings 86 and 90 when the contacts 54 and 63 of switch 36 are together; and this circuit is broken when those contacts are separated due to the action of centrifugal force. An electrical circuit is similarly made and broken between slip rings 88 and 90 when the contacts 54 and 63 of switch 38 are to gether or separated under centrifugal force.

While many variations'are possible, it'is intended in the disclosure above-described that the switch designated 36 in Fig. 1 would be a normally open switch, with its snapover contact 52 abutting against stop 48 and separated from follow-up contact 63 due to centrifugal force at the desired speed of rotation, and closing with contact 63 when the angular velocity of shaft 34 is reduced below a predetermined value. Also, the switch designated 38 would be a normally closed switch at the desired rotational speed of shaft 34 and would open when the angular velocity of shaft 34 exceeded a predeter; mined value. Thus, for example, the described gover nor switch device 30 has actually been used to control rotation of a shaft between 11,750 and 12,000 rpm. In such installation, below 11,750 rpm, switches 36 and 38 are both closed; between 11,750 and 12,000 rpm, switch 36 is open and switch 38 is closed; and above 12,000 r.p.m. both switches 36 and 38 are open. In a typical installation the switches 36 and 38 of centrifugal control device 30 are suitably wired in the control system in a manner known in the art.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

It is claimed and desired to secure by Letters Patent;

1. A centrifugal governor switch device comprising: operating contact means adapted to be normally disposed towards an axis about which the device moves in an armate path, a mounting for said contact means to permit movement thereof away from said axis through snapover position under centrifugal force; follow-up contact means operably disposed adjacent said operating contact means and being movable under centrifugal force in engagement with said operating contact means for part of its travel, and means operably connected to said follow-up contact means and restraining movement thereof after the operating contact means moves through snapover position.

2. A centrifugal snapover switch device as defined ii claim 1, further comprising back-up means operably engaging said follow-up contact means for maintaining the follow-up contact means in engagement with the operating contact means when the switch is in static position.

3. A centrifugal governor switch device as defined in claim 1, wherein the follow-up contact means has a higher mass than the operating contact means, thereby providing high contact pressure up to the snapover position.

4. A centrifugal governor switch device as defined in claim 1, further comprising adjustable stop means carried by said mounting for changing the total travel of said operating contact means between its position closest to said axis and its extreme snapover position away from said axis.

5. A centrifugal governor switch device as defined in claim 1, further comprising adjusting means operably engaging said mounting for varying the angular velocity at which the operating contact means moves through snapover position under centrifugal force.

6. A centrifugal governor switch device as defined in claim 1, further comprising adjusting means operably e'ria gaging the restraining means on said follow-up contact means for varying the extent the follow-up contact means iollows the operating contact means under centrifugal orce.

7. A centrifugal snap acting switch device including a base with a part thereof adapted to be mounted on a rotating shaft, and at least one centrifugal snap acting switch on said base comprising: an operating contact blade having a contact thereon, normally biased towards said shaft mounting part of the base and movable through snapover position under centrifugal force; a follow-up contact blade having a contact thereon in operative association with said first-mentioned contact, said follow-up blade and contact being movable under the action of centrifugal force so that the follow-up contact stays in engagement with said first-mentioned contact for at least a part of its travel; and means for controlling movement of the follow-up blade so that the follow-up contact is stopped substantially at the snapover position of the firstmentioned contact.

8. A snapover governor switch device as defined in claim 7 further comprising a resilient member disposed adjacent the follow-up blade and maintaining said followup contact in engagement with said first-mentioned contact when the switch device is in static condition.

9. A centrifugal snap acting governor switch device including a base with a part thereof adapted to be mounted on a rotating shaft, and at least one centrifugally operated snap acting switch comprising: support means on said base having a pair of spaced legs; an operating snapover blade supported by said spaced legs, said operating blade being biased toward said shaft-mounting part of the base and carrying a contact thereon positioned substantially radially of said axis, whereby said snapover contact is movable through snapover position under centrifugal force; a follow-up contact blade mounted on a support means on said body, with a contact thereon positioned substantially radially of said axis in operative association with said first-mentioned contact, one end of said follow-up blade being fixed to said support means and the other end of said operating blade being movable with respect thereto so that the follow-up blade is movable with said snapover operating blade under centrifugal force and remains in engagement therewith for part of its travel; and means for restraining the movable end of the follow-up blade so that the follow-up contact does not follow the snapover contact through the snapover positron.

10. A centrifugal snap acting governor switch device as defined in claim. 9, further including a leaf spring mounted on said base adjacent the follow-up contact biade and disposed between it and said shaft-mounting part of the base, said leaf spring engaging the follow-up contact and urging it into engagement with the snapover contact when the governor switch device is in static condition.

ll. A centrifugal snap acting governor switch device as defined in claim 9 further comprising: first adjustment means for varying the total travel of said snapover contact between its position closest to said shaft-mounting part and its extreme snapover position away therefrom; second adjustment means for changing the distance between said legs supporting the snapover contact blade to change the bias of said blade and thereby change the angular velocity at which said blade is actuated through snapover position as a result of centrifugal force; and third adjusting means for varying the extent that the follow-up contact moves together with the operating snapover contact under the action of centrifugal force.

12. A snap acting switch device comprising: an operating contact blade having a contact thereon normally biased towards a first position and movable under an applied force through snapover position to a second position; a follow-up contact blade having a contact thereon in operative association with said first-mentioned contact in said first position, said follow-up blade being movable so that the follow-up contact stays in engagement with said first-mentioned contact for at least a part of its travel under the action of said force; and means operably associated with said follow-up blade for controlling movement of the follow-up blade so that the follow-up contact is stopped substantially at the snapover position of the first-mentioned contact.

References Cited in the file of this patent UNITED STATES PATENTS 1,663,207 Mallory Mar. 20, 1928 FOREIGN PATENTS 243,439 Switzerland Dec. 16, 1946 478,398 Germany June 24, 1929 

